This invention relates to a process for restarting a tool onto a workpiece contour after a program interruption. This invention is particularly directed for use with a numerically controlled processing machine of the type which comprises a controller, a display unit for graphically representing processing information, and means for storing a plurality of program sets which combine to form a processing program, each program set representing a respective contour section of the workpiece contour to be produced.
German Pat. DE-PS No. 26 42 453 discloses a process for restarting a changed tool from a defined position onto a workpiece after a program interruption in a computer-controlled machine tool. The program is restarted with new tool correction values from a proscribed starting point and is executed in a control mode, without machine movement, up to an end point to which is allocated a corrected starting point for the tool. The tool is thereupon automatically driven back on a path between the defined position and the corrected starting point.
This process, however, presents the disadvantage that it is in general difficult to determine an appropriate end point, especially in the case of complicated programs that present, for example, several subprogram sets or program partial repetitions.